When a workload analysis of a storage device such as an HDD (Hard Disk Drive) is performed, a load is often biased to some areas. FIG. 14 is an example of a workload analysis. In FIG. 14, the vertical axis indicates an offset in a downward direction and the horizontal axis indicates an elapsed time. The offset represents a difference from a head address of a volume allocated to a user. The elapsed time is measured in the unit of minutes.
In FIG. 14, the black part is a high load area. Three blocks are present as the high load area in FIG. 14. Among the high load areas, for an area that is generated similarly on a daily basis, static hierarchical control is effective. The static hierarchical control is a technique of moving data of a high load area to a storage device such as an SSD (Solid State Drive), which works at a speed higher than that of an HDD, by using previous statistical information at a pre-determined time on a daily basis.
For example, in FIG. 14, when a block A and a block B among the three blocks are generated similarly on a daily basis, data corresponding to the blocks A and B are moved to an SSD, so that frequently accessed data is accessed at a high speed. Therefore, by using the static hierarchical control, the performance of an information processing system can be improved.
Meanwhile, in FIG. 14, when a block C is generated only on a particular day, the block C cannot be moved to the SSD by using the static hierarchical control. Accordingly, dynamic hierarchical control that moves data of a high load area to the SSD based on a load that is measured in real time is executed on the block C (see, for example, Kazuichi Oe, Kazutaka Ogihara, Yasuo Noguchi, and Toshihiro Ozawa, “Proposal for a hierarchical storage system that can move a spike to high-speed storage in real time”, the Annual Symposium on Advanced Computing Systems and Infrastructures (SACSIS2012), Kobe, Japan, May 2012).
There has been a conventional technique in which, when a highly-frequently accessed file is accessed, based on related information such as a sector used by the file, a disk array device reads data that is stored in a sector in a predetermined neighborhood of the sector used by the file in a hard disk into a cache. Furthermore, there has been a conventional technique of, when a presence density that is the rate at which an accessed logical track is present is increased or equal to or larger than a certain value, determining as sequential access or generally sequential access and pre-reading a neighborhood of a block in which data is present from an external storage device. Further, there has been a conventional technique in which, in a disk control device including a cache, a neighboring part of an accessed physical area is also loaded.    Patent Document 1: Japanese Laid-open Patent Publication No. 2002-207620    Patent Document 2: Japanese Laid-open Patent Publication No. 2002-182978    Patent Document 3: Japanese Laid-open Patent Publication No. 06-119244
By applying the conventional techniques of moving data of a neighborhood of a high load area to dynamic hierarchical control that moves data of a high load area to an SSD based on a load measured in real time, the performance of an information processing system can be improved. However, in order to move the data of the neighborhood of the high load area to the SSD, an area that is appropriate as the neighborhood needs to be selected.